The president of a company that builds anatomical skeletons for schools and laboratories is being investigated by Japanese police after they found the remains of as many as 500 people in the garden of a building used by the company.

The building in question belonged to one of his employees and doubled up as an office for the Habara Skeleton Specimen Research Institute. However, this employee died due to illness last November, leading police to discover a huge number of human bones in his backyard.

The discovery of the bones in Tokyo’s Adachi Ward was first reported by Japanese newspapers back in February.

“An officer dispatched to the home found large amounts of bones inside and in the yard,” wrote Shota Harumashi and Yoshitaka Yamamoto for the Mainichi Shimbun. “The bones were later identified as human.”

Now, the man in charge of the company is being questioned, and has been reported to public prosecutors by police. The man has not been named as he has not yet been charged, and is accused of illegally dumping the human bones in the garden a number of years ago and violating Japan’s Waste Management and Public Cleansing Act.

The Metropolitan Police Department’s Nishiarai Police Station accused the man in papers sent to public prosecutors on April 9, the Mainichi Shimbun reports. He has apparently admitted to the allegations.

So where did the bones come from? The skeletal remains were apparently brought to Japan from India a few decades back, a person connected to the investigation told police. Before the 1970s, it was common practice for Japanese companies to use real human bones to build anatomical skeletons for schools, universities, and laboratories, The Telegraph reports. 

India used to be the world's leading exporter of human bones for medical study, but the practice was outlawed in 1985. Many skeletons were robbed from graves and the country exported a vast 60,000 skulls the year before the ban came into place, reports the Chicago Tribune. Now, stolen bones can still be purchased on the black market. Just a couple of years ago, Indian police arrested eight people suspected of smuggling stolen bones in West Bengal. 

Japanese police will now investigate exactly how the company managed to import the human remains from India and potentially assess whether other similar companies are also involved in the illegal disposal of human bones. Unfortunately, it is unlikely that the identities of the people that the bones belong to will ever be determined.